"Not only did transport inflation - airfares in particular - not fall all the way back after last month's Easter-related jump, but food price inflation also rose a bit more sharply than we had expected," said Jonathan Loynes of Capital Economics.

"Further rises in the latter, along with recently announced further energy price hikes, are likely to take the headline inflation rate above 5% perhaps, and perhaps even above 5.5%."

Last week, Scottish Power - which supplies 2.4 million UK households - said it would increase the cost of gas by 19% and the cost of electricity by 10% from 1 August.

The Bank of England has resisted calls to raise interest rates - seen as the most effective policy tool in combating inflation - on the basis that temporary, external factors, such as rising oil and food costs, are driving price rises.

People on lower incomes spend a higher proportion of their money on gas, electricity and food, the cost of which has risen sharply, while those on higher incomes have benefited more from lower mortgage rates.

"Many workers have had no pay increase this year and even those who have are finding their household budgets stretched to breaking point, as prices rise twice as fast as pay," said Brendan Barber, general secretary of the TUC.

"But raising interest rates now would only make matters worse."

Among those hardest hit by the continuing high rate of inflation are savers.

The effect of inflation on savings means that £10,000 invested five years ago, allowing for average interest, inflation and tax at 20% would have the spending power of just £9,441 today, according to financial information service Moneyfacts.

"Rising inflation means hundreds of thousands of savers need accounts paying a staggering 5.63% before they earn a real rate of return on their savings," said Sylvia Waycot from financial information service Moneyfacts.

"This is going to be pretty difficult bearing in mind the average interest offered on an easy access savings account is 0.89%."

Basic rate taxpayers have just one account, a fixed rate Isa, which negates the effects of CPI inflation, according to Moneyfacts. There are no fixed rate accounts available for any taxpayer that beats RPI inflation.